The invention relates to a method and a device for cutting yarn on a textile machine, with a blade, the blade being supplied with kinetic energy via a drive.
Devices of this type are more particularly arranged on textile machines, such as winding machines for example. Here, they are provided for cutting out faults, such as thick or thin areas in the yarn for example. The cutting is effected by means of a displaceably mounted blade, which forces the yarn against a brace and, once the yarn is resting against the brace, cuts said yarn. To this end, it is necessary for the blade to absorb sufficient kinetic energy before contacting the yarn. In this respect, it is usual to accelerate the blade to such a degree that it can rapidly cut through all conceivable yarns with its kinetic energy. Excess energy is dispelled on the brace. Or, the blade receives the amount of energy which is currently available depending on the given circumstances. In this case, the amount of energy supplied to the blade can vary arbitrarily.
In known devices, plunger-type or tilting armatures are used for the drive, the blade being connected to the armature.
A disadvantage of these known devices can be seen in that the cutting force of the blade is designed for the thickest yarn which is likely to be processed by the device, or the drive quite simply transmits its full power at all times, or the amount of power available at any one time. Practically, this results in the blade being excessively or too rapidly worn and in the device as a whole experiencing unnecessarily high vibrations.
It is therefore the object of the invention to provide a method and apparatus which avoids these disadvantages and which always produces sufficient cutting force.
This is attained in that the kinetic energy is supplied in metered fashion and is measured as a function of a property from a group. This group comprises properties of the material from which the yarn is made, diameter, cross section, mass of the yarn, etc., as well as properties which are used for the cutting. One such property, for example, is the inertia of the mass displaced with the blade and of the blade per se, the characteristic of the frictional resistance of the moved blade etc.. A property such as the diameter, for example, or the cross section of the yarn is preferably measured directly prior to cutting, i.e. continuously, and the measured value is taken into account when measuring the supplied energy. Consequently, the drive comprises a device for measuring the kinetic energy of the blade.
The advantages which are hereby obtained can be seen in particular in that the blade, the brace or the anvil and in fact the entire device with the suspension is protected. In addition, undesirable secondary effects are prevented, such as excessive springing back of the blade, which impacts the brace with excessive surplus energy. Since the measurement of the kinetic energy can result in a restriction as well as an increase in the voltage applied to the drive, it is possible to carry out perfect cutting of the yarn even if the textile machine supplies insufficient voltage to the device.